The incidence and stability over time of sleep disturbance, based on mothers' reports, are examined in children whose mothers have a diagnosis of bipolar depression, children whose mothers have a diagnosis of unipolar depression, and well mothers. Mothers' reports were obtained twice on two of their children: (a) on the younger children when they were between 2 and 3 1/2 years old and again when they were between 5 and 6 1/2 years old: and (b) on the older children when they were between 5 and 8 years old and again when they were between 8 and 11 years old. In addition, sleep problems in these children are examined in relation to incidence of depression in parents; i.e., in children who have two depressed parents, children who have one depressed parent, and children who have no depressed parents.